First principles molecular dynamics study of amorphous Si\sub{1-x}Ge\sub{x}:H alloys

TL;DR

This study uses first principles molecular dynamics to analyze how varying Ge content affects the structure, defects, and electronic properties of amorphous Si:H alloys, revealing increased defects and decreased band-gap with more Ge.

Contribution

It provides detailed insights into the structural and electronic evolution of amorphous Si:Ge:H alloys with changing Ge concentration using first principles simulations.

Findings

Increased Ge content leads to more network defects.

Band-gap decreases as Ge concentration increases.

Electronic density of states shows exponential Urbach tail behavior.

Abstract

We study the structural, dynamical and electronic properties of amorphous Si\sub{1-x}Ge\sub{x}:H alloys using first principles local basis molecular dynamics simulation. The network topology and defects in the amorphous network have been analyzed. Structural changes and an increase in number of defects have been found as the Ge atomic percentage increases from x=0.1 to x=0.5. The electronic density of states exhibits a decreasing band-gap and increased mid-gap and band-tail defect states as Ge concentration increases. Investigation of the band tails of the density of states show an exponential (Urbach) behavior. The mobility gap is estimated as a function of Ge concentration.